Sandbox Reserved 193: Difference between revisions
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== INCL == | == INCL == | ||
Various mutations have been found in INCL patients ( Hofmann S L, Das A K, Yi W, Lu J-Y, Wisniewski K E. Mol Genet Metab. 1999;66:234–239. [PubMed]Das A K, Becerra C H R, Yi W, Lu J-Y, Siakotos A N, Wisniewski K N, Hofmann S L. J Clin Invest. 1998;102:361–370. [PMC free article] [PubMed]). Most of these mutations are caused by nonsense or missense mutations within close proximity to the catalytic triad. These mutations lead to an inactive PPT1 enzyme as they are predicted to create unfavorable steric, polar, and electrostatic interactions that could disturb the nucleophilic elbow. The nucleophilic elbow is responsible for proper location and orientation of the Ser 115 (part of the catalytic triad link?). Catalytic ability would be greatly reduced if the original position of Ser115 was altered because it must be properly orientated to be activated by His289 (part of the catalytic triad Link?) in order to attack the substrate. One example of mutation such as <scene name='58/580837/Methionine/ | Various mutations have been found in INCL patients ( Hofmann S L, Das A K, Yi W, Lu J-Y, Wisniewski K E. Mol Genet Metab. 1999;66:234–239. [PubMed]Das A K, Becerra C H R, Yi W, Lu J-Y, Siakotos A N, Wisniewski K N, Hofmann S L. J Clin Invest. 1998;102:361–370. [PMC free article] [PubMed]). Most of these mutations are caused by nonsense or missense mutations within close proximity to the catalytic triad. These mutations lead to an inactive PPT1 enzyme as they are predicted to create unfavorable steric, polar, and electrostatic interactions that could disturb the nucleophilic elbow. The nucleophilic elbow is responsible for proper location and orientation of the Ser 115 (part of the catalytic triad link?). Catalytic ability would be greatly reduced if the original position of Ser115 was altered because it must be properly orientated to be activated by His289 (part of the catalytic triad Link?) in order to attack the substrate. One example of mutation such as <scene name='58/580837/Methionine/3'>Val181Met</scene> and <scene name='58/580837/Lysine_mutation/2'>Glu184Lys</scene> give a good depiction of how the increase in size in the mutated amino acids and positive charge on lysine mutation would create steric and polar clashes with the adjacent helices of the binding pocket compared to the <scene name='58/580837/Val181glu184/2'>Normal Val181 & Glu184</scene> <scene name='58/580837/Arginine_fine/2'>Normal Arg122</scene> which is described in more detail below. | ||
Known INCL Mutations | Known INCL Mutations | ||
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== LINCL == | == LINCL == | ||
LINCl is caused by a mutation in the CLN2 gene which “codes for a lysosomal pepstatin-insensitive acid protease that is deficient in LINCL patients” (Vines D J, Warburton M J. FEBS Lett. 1999;443:131–135. [PubMed]. Mutations that tend to lead to LINCL still disrupt the active site and binding pocket geometry but do not do it to the degree that is seen in INCL. One LINCL mutation is <scene name='58/580837/Multiple_mutations_mutating/3'>Gln177Glu | LINCl is caused by a mutation in the CLN2 gene which “codes for a lysosomal pepstatin-insensitive acid protease that is deficient in LINCL patients” (Vines D J, Warburton M J. FEBS Lett. 1999;443:131–135. [PubMed]. Mutations that tend to lead to LINCL still disrupt the active site and binding pocket geometry but do not do it to the degree that is seen in INCL. One LINCL mutation is <scene name='58/580837/Multiple_mutations_mutating/3'>Gln177Glu</scene>. The <scene name='58/580837/Multiple_mutations/3'>Gln177</scene> acts as a hydrogen bond donor to Ala171 and Ala183 and as a hydrogen bond acceptor from Ile200. It is presumed that the mutation to Glu177 would cause a conformation change of the helices in the area. Ala171 and Ala183 make hydrophobic contact with the palmitate, and so the altered conformation associated with those two amino acids would decrease binding affinity of the palmitate, decreasing the catalytic activity but not to the extent of the mutations seen in INCL. | ||
== JNCL == | == JNCL == | ||
JNCL is caused by a mutation in the CLN3 gene which codes for a lysosomal membrane protein of unknown function (Lerner T J, Boustany R N, Anderson J W, D'Arigo K D, Schlumpf K, Buckler A J, Gusella J F, Haines J L, Kremmidiotis G, Lensink I L, et al. Cell. 1995;82:949–957.). Unlike the mutations that cause INCL and LINCL, mutations that lead to JNCL are located away from the active site and are seen to cause less damage to the overall structure of PPT1. Some of the mutations in JNCL have been noted as retaining a low level of PPT1 activity as the catalytic site is left fairly unperturbed. Mutations associated with JNCl are found in two locations, Thr75Pro with Asp79Gly and <scene name='58/580837/Juvenile_mutation/1'>Tyr247His with Gly250Val</scene>. These mutations are predicted to disturb the geometry of α1, increase the flexibility of the region, and alter the antiparallel βsheet motif in βa and βb compared to the | JNCL is caused by a mutation in the CLN3 gene which codes for a lysosomal membrane protein of unknown function (Lerner T J, Boustany R N, Anderson J W, D'Arigo K D, Schlumpf K, Buckler A J, Gusella J F, Haines J L, Kremmidiotis G, Lensink I L, et al. Cell. 1995;82:949–957.). Unlike the mutations that cause INCL and LINCL, mutations that lead to JNCL are located away from the active site and are seen to cause less damage to the overall structure of PPT1. Some of the mutations in JNCL have been noted as retaining a low level of PPT1 activity as the catalytic site is left fairly unperturbed. Mutations associated with JNCl are found in two locations, Thr75Pro with Asp79Gly and <scene name='58/580837/Juvenile_mutation/1'>Tyr247His with Gly250Val</scene>. These mutations are predicted to disturb the geometry of α1, increase the flexibility of the region, and alter the antiparallel βsheet motif in βa and βb compared to the | ||
<scene name='58/580837/Tyrosine_normal/1'> | <scene name='58/580837/Tyrosine_normal/1'>Normal Tyr247 & Gly250</scene>. | ||
